In the field of graphic arts, it has been strongly desired to conduct complicated operations (particularly contact-printing procedures (commonly called "contact work")) under bright circumstances. As one technique for meeting this desire, silver halide photographic light-sensitive materials have been developed which do not cause serious fog when handled for a long time under safelight having a wavelength of yellow or longer than yellow light (that is, yellow lamps, bright green lamps, bright red lamps, etc.; since yellow lamps are brightest, the safelight will be represented by yellow safelight hereinafter).
However, as a result of giving special weight to prevention of fog formation under safelight, conventional light-sensitive materials for photomechanical process to be handled under yellow safelight have low sensitivity for light of the exposure wavelength region and show somewhat unsatisfactory photographic properties.
In order to enhance sensitivity of silver halide photographic light-sensitive materials, techniques have been employed of strengthening the degree of chemical sensitization (e.g., reduction sensitization, noble metal sensitization, sulfur sensitization, etc.), and/or using spectral sensitizing dyes.
However, excessive strengthening of the chemical sensitization results in extremely increased fog and deteriorated preservability, and hence sensitivity of light-sensitive materials for photomechanical process to be handled under safelight cannot be fully enhanced by this technique only.
Thus, it is considered desirable to enhance spectral sensitivity to light of the exposure wavelength region, particularly blue light, by using sensitizing dyes. Many blue-region spectrally sensitizing dyes have a side absorption in the yellow safelight wavelength region (e.g. light that has been filtered with Kodak Safelight Filter OA Kodak Safelight Filter OO, both made by Eastman Kodak Co.), and hence they have the defects of causing fog or having no adaptability for rapid access type developers for obtaining contrasty photographic properties (i.e., having a gamma value of more than 3), infectious developers, contrasty developers described in U.S. Pat. No. 4,452,882 corresponding to Japanese Patent Application (OPI) No. 190,943/83 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application"), etc., thus not being practically usable.